Spray coating is a fairly diverse art. In some applications spray coating is done in the atmosphere, while in other applications it is performed in a chamber which is substantially closed, except perhaps for openings through which a product to be coated can be conveyed. Other openings into or out of the spray booth may also be present.
In some of the coating operations done in a chamber air can be tolerated in the chamber, while in other applications a solvent rich atmosphere is maintained.
In coating booths utilizing a solvent rich atmosphere, the coating material is generally atomized hydraulically and directed onto a substrate to be coated. By hydraulic atomization, it is meant that the coating material is atomized by means of a special type of orifice through which coating material is pumped at a high hydraulic pressure on the order of 300 to 3000 psi. No compressed gas is generally used in such systems to effect the atomization. When the coating material is sprayed some of the solvent present in the coating material evaporates upon discharge from the nozzle. Shortly, the solvent vapors displace any air which is in the interior of the coating chamber and provide a solvent rich atmosphere.
Solvent rich atmosphere coaters result in a condition within the spray booth where oversprayed material does not solidify on the interior of the chamber walls, or other interior surfaces. Such coaters exhibit other advantageous results known to those skilled in the art.
Of necessity, most coating booths have openings in them, for example, the opening through which a product to be coated is conveyed. Such is usually true of the coaters utilizing a solvent rich atmosphere, and as these processes are generally continuous operations, the solvent vapors which are being added to the atmosphere of the coater must be removed lest they escape through any openings into or out of the coating chamber. The vapors and contaminated atmosphere removed can then be filtered or recycled or both.
It is significant to note that any exhaust system used to prevent the vapors from escaping from the openings in a booth having a solvent rich atmosphere, need not and usually should not create a large amount of vapor flow. A large amount of vacuum or vapor flow would result in a condition where air could be drawn into the coating chamber whereupon the advantages of the solvent rich atmosphere would be defeated.
Prior art methods of preventing the vapors from issuing through the holes were inadequate for many applications. Many systems provided too much vacuum, and hence excessive flow volume from the chamber for certain applications, such as solvent rich atmosphere coaters. Other systems were built into the chamber itself and were difficult if not impossible to add to an existing system. Further, many of these prior art devices were bulky and required an excessive amount of space for installation. Further, the prior art devices were rather complex structures, both in terms of their mode of operation, and assembly. Further, complex assembly procedures added expense to the manufacture of such devices.
The present invention provides an improved manifold assembly for containing the vapors which might issue from a coating chamber. Various aspects of the present invention combine to result in a maifold which is simple in its design and air flow characteristics, and can provide good controllability of small negative pressures to result in small air flow volumes necessary to many applications. Further, various aspects combine to provide a compact, less complex, and less costly device which can be easily added to existing coating chambers.
Although the present invention has particular application to coating booths having a solvent rich atmosphere, it will be recognized by those skilled in the art that the manifold of the present invention will have uses in conjunction with other types of booths having a contaminated atmosphere as well.
The manifold comprises a front wall and a rear wall, both having apertures therethrough leading to an opening into or out of the coater. A side wall assembly is provided and attached to the front and rear walls to form a hollow chamber around the apertures. A collar is provided around the aperture and is attached to the front and rear walls. It is constructed so as to have or form holes therethrough to allow vapors issuing out of the opening in the coating chamber to be drawn into the manifold. Baffle means are provided in the manifold chamber creating a generally downward then upward vapor flow passage from and generally around the collar. A spray nozzle adapted to spray a precipitant such as water in a generally downward direction in the vapor flow passage is provided to create a venturi effect in the vapor flow passage which causes vapors to be drawn into the manifold. The sprayed precipitant also acts to scrub the vapors drawn through the air flow passage and cause paint particles and other contaminants to be precipitated out of the vapor. Drain means are provided at the lower portion of the chamber to remove the precipitants and precipitated contaminants. An exhaust port for the scrubbed vapors is provided in the vapor flow passage and is located above the drain means and downstream of the spray nozzle.